It is necessary in a variety of fields to mix fluids that have separated from each other after being stored in a container for a period of time. Prior art mixers generally operate using one of a limited number of mixing actions such as, for example, rapid up/down movement or shaking of the container, rotation of the container in opposite directions, and rocking devices which tilt the container back and forth. The mixing effectiveness of these conventional mixing devices can often be enhanced by placing mixing beads or bars within the vessel so that the beads or bars are propelled through the fluid by the mixing action.
Regardless of which conventional technique is used, mixing devices are generally incapable of occupying a small Space, using a minimum of power and mixing rapidly without the aid of a mixing bead or other object within the container.
One application in which a compact, low power, and highly effective mixing device is required is to mix calibrating and washing fluids in a blood sampling cartridge of the type described and claimed in U.S. Pat. No. 5,143,084, which is incorporated herein by reference. As disclosed in U.S. Pat. No. 5,143,084, a sampling cartridge contains a body fluid storage chamber in which a body fluid, such as blood, is collected. The cartridge interfaces with an analysis system that receives the body fluid from the body fluid chamber as well as washing and calibrating fluids from ampules that form part of the cartridge. The fluids in the ampules become separated from each other in storage, and the fluids in each of the ampules must thus be mixed prior to flowing into the analysis system. The mixing device should be incorporated into the analysis system, and it is important that doing so does not unduly increase the size, weight, power requirements or price of the analysis system. Furthermore, since the analysis system must rapidly analyze samples, it is important that the mixing device be highly efficient in quickly providing substantially complete mixing of the fluids in each of the ampules. As a result, there has not heretofore been available a mixing device that is ideally suited for use in an analysis system that interfaces with body fluid sampling cartridges of the type disclosed in U.S. Pat. No. 5,143,084.